Gas dynamic lasers

Abstract

In a high-power laser system it is proposed that combustion or compressor gases be diverted from the normal flow path through a gas turbine engine into an auxiliary flowpath, and that their composition be subsequently adjusted by burning at least one hydrocarbon fuel in them and possibly also by adding other fuels and substances. Suitable aerodynamic expansion of the resultant gases produces a population inversion in the CO 2 species, which can be utilized in a laser.

We claim: 
     
       1. A method of operating a combustion powered air-breathing gas dynamic laser of the carbon dioxide type by taking gases from a continuous combustion engine,   burning in said engine gases at least one fuel to produce a gaseous mixture for lasing, and   passing said gaseous mixture through said laser; said continuous combustion engine being a gas turbine engine, said gases taken from said engine being diverted from the normal flow path therethrough into an auxiliary flow path including therein said laser, said at least one fuel including at least one hydrocarbon fuel whereby the gaseous H 2  O:CO 2  ratio in the combustion gases is caused to be in the range between 2:1 and 1:11.5, and said gaseous mixture being lased by aerodynamically expanding said mixture supersonically and passing it through an optically resonant cavity.   
     
     
       2. A method according to claim 1 in which the diverted engine gases are taken from the compressor section of the gas turbine engine. 
     
     
       3. A method according to claim 1 in which the diverted engine gases are combustion gases from the gas turbine engine. 
     
     
       4. A method according to claim 2 in which the engine gases are passed to a reservoir/combustion chamber wherein the hydrocarbon fuel is burnt. 
     
     
       5. A method according to claim 4 in which one or more further substances are introduced into the reservoir/combustion chamber, said further substances being selected from the group comprising further hydrocarbon fuels, hydrogen, carbon monoxide, carbon disulphide, cyanogen, nitrogen and carbon dioxide. 
     
     
       6. A method according to claim 3 in which the diverted engine gases are passed for further combustion to a reservoir/combustion chamber wherein the hydrocarbon fuel is burnt. 
     
     
       7. A method according to claim 6 in which one or more further substances are introduced into the reservoir/combustion chamber, said further substances being selected from the group comprising further hydrocarbon fuels, hydrogen, carbon monoxide, carbon disulphide, cyanogen, finely divided carbon, air, nitrogen and carbon dioxide. 
     
     
       8. A method according to claim 1 in which, besides the hydrocarbon fuel, one or more further substances are introduced into the diverted engine gases, said further substances being selected from the group comprising further hydrocarbon fuels, hydrogen, carbon monoxide, carbon disulphide, cyanogen, finely divided carbon, air, nitrogen and carbon dioxide. 
     
     
       9. A method according to claim 1 in which, after passing through the optically resonant cavity, the gases are exhausted to the gas turbine engine exhaust duct. 
     
     
       10. A method according to claim 1 in which, after passing through the optically resonant cavity, the gases are exhausted to atmosphere. 
     
     
       11. A combustion powered air breathing gas dynamic laser system of the carbon dioxide type including in flow sequence a continuous combustion engine,   means for taking gases from said engine,   means for burning at least one fuel in said engine gases to produce a gaseous mixture for lasing,   a gas dynamic laser, and   means for exhausting said gaseous mixture from said laser after passage therethrough; said continuous combustion engine being a gas turbine engine, said means for taking gases from said engine being adapted to divert said gases from their normal flow path therethrough into an auxiliary flow path including therein said laser, said at least one fuel including at least one hydrocarbon fuel whereby the gaseous H 2  O:CO 2  ratio in the combustion gases is caused to be in the range between 2:1 and 1:11.5, and said laser including means for aerodynamically expanding said mixture supersonically and an optically resonant cavity for stimulating lasing in said mixture.   
     
     
       12. A system according to claim 11 in which the diverted engine gases are taken from the compressor section of the gas turbine engine. 
     
     
       13. A system according to claim 11 in which the diverted engine gases taken from the gas turbine engine are combustion gases of said engine. 
     
     
       14. A system according to claim 12 in which the auxiliary flow path includes a reservoir/combustion chamber located upstream of the laser, said chamber having means for introducing the hydrocarbon fuel into the diverted engine gases and burning said hydrocarbon fuel therein. 
     
     
       15. A system according to claim 14 having means through which one or more further substances are introduced into the combustion chamber, said further substances being selected from the group comprising further hydrocarbon fuels, hydrogen, carbon monoxide, carbon disulphide, cyanogen, nitrogen and carbon dioxide. 
     
     
       16. A system according to claim 13 in which the auxiliary flow path includes a reservoir/combustion chamber located upstream of the laser, said chamber having means for introducing the hydrocarbon fuel into the diverted engine gases and burning said hydrocarbon fuel therein. 
     
     
       17. A system according to claim 16 having means through which one or more further substances are introduced into the reservoir/combustion chamber, said further substances being selected from the group comprising further hydrocarbon fuels, hydrogen, carbon monoxide, carbon disulphide, cyanogen, finely divided carbon, air, nitrogen and carbon dioxide. 
     
     
       18. A system according to claim 11 having, besides means for burning the hydrocarbon fuel in the engine gases, means for introducing one or more further substances into said engine gases, said further substances being selected from the group comprising further hydrocarbon fuels, hydrogen, carbon monoxide, carbon disulphide, cyanogen, finely divided carbon, air, nitrogen and carbon dioxide. 
     
     
       19. A system according to claim 11 in which means for aerodynamically expanding the gaseous mixture comprise a plurality of convergent-divergent supersonic expansion nozzles. 
     
     
       20. A system according to claim 19 in which the expansion nozzles comprise a plurality of spaced-apart aerodynamically shaped vanes. 
     
     
       21. A system according to claim 11 in which means for aerodynamically expanding the gaseous mixture comprises at least one row of aerodynamically shaped vanes forming a supersonic turning nozzle adapted to both supersonically expand the gaseous mixture and change its direction of flow before its entry into the optically resonant cavity. 
     
     
       22. A system according to claim 11 in which the means whereby the gaseous mixture is exhausted from the laser comprises at least compressor means operable to remove said mixture from the optically resonant cavity and pass it to the exhaust duct of the gas turbine engine. 
     
     
       23. A system according to claim 11 in which the means whereby the gaseous mixture is exhausted from the laser comprises at least compressor means operable to remove said mixture from the optically resonant cavity and pass it to atmosphere. 
     
     
       24. A system according to claim 11 in which the means whereby the gaseous mixture is exhausted from the laser comprises a diffuser adapted to pass gases to the exhaust duct of the gas turbine. 
     
     
       25. A system according to claim 11 in which the means whereby the gaseous mixture is exhausted from the laser comprises a diffuser adapted to pass gases to atmosphere. 
     
     
       26. The method of claim 1 wherein the ratio of H 2  O to CO 2  is in the range of between 2:1 and 1:2. 
     
     
       27. The system of claim 11 wherein the ratio of H 2  O to CO 2  is in the range of between 2:1 and 1:2. 
     
     
       28. The system of claim 11 wherein said means for aerodynamically expanding said mixture supersonically comprises a plurality of supersonic expansion nozzles having an area ratio of at least 50:1. 
     
     
       29. The system of claim 19 wherein the area ratio of said supersonic expansion nozzles is at least 50:1.